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DVI-D to VGA converter for Beagleboard-xM

For a long time I tried to find cheap and high quality DVI-D to VGA converter in order to connect BB-xM to my old VGA monitor. And I found such converter!It’s a fit-VGA converter from fit-PC2 guys. It costs 44.69 AUD (with GST) in Sydney and you can buy it here. This converter is definitely the best solution for these money as it has only active components for converting DVI-D signal to analog VGA. The main chip is TFP401A PanelBus DVI Receiver(Texas Instruments) plus a FMS3818 triple D/A converter (Fairchild Semiconductor).

However, in order to use this converter with Beagleboard you have to make a small modification. BB has RT1 PolySwitch RXEF010 (Tyco Electronics) with steady current = 0.1 A and trip current = 0.2 A. This little yellow guy sits between DVI-D and S-Video connectors and limits current through the DVI port but according to the TFP401A datasheet “IDD(2PIX) Normal 2-pix/clock power supply current” is equal to 370 mA which is more than 0.2 A trip current for RXEF010. That is why I saw my monitor going to the power saving mode after a minute of using fit-VGA with resolution 1024×768. After that I bought on ebay PolySwitch RXEF025 (steady current = 0.25 A, trip current = 0.5 A) and replaced RT1 with the new one. And now fit-VGA works perfect!!!

P.S. Probably, you can just replace RT1 with a piece of wire (connect DVI port directly to the U32 FDC6330L Integrated Load Switch from Fairchild Semiconductor) but it’s better to have additional protection from overcurrent.

I've bought the Beagle Board Rev. C4 and the fit-vga converter. As soon as I attached the converter to the hdmi port of the beagle board I saw a yellow image for 10 seconds and then the monitor is turned off. Do you know if the converter will work with the PolySwitch RXEF025 ?

See the very last page of PDF document. RT1 element is a polyswitch. One end is connected to the +5V, another to the DVI-D interface, pin 7 of U11 (TXS0102) and C125 capasitor. After your monitor is turned off (i.e. after 10 seconds) please measure voltage on pin 7 of U11. If you can't see any voltage then you have some problems with overcurrent. I'm not sure it's normal as RXEF025 has 250 mA steady current and 500 mA trip current which is enough for normal operation of TFP401A.

I used your blog as a reference and purchased the 2 components required to perform the necessary conversion (fit-VGA and RXEF025 fuse). First I tried the fitVGA without replacing the fuse on the BBxM, the display worked for a minute and then went off. That I was expecting, since another user above (Marietto) reported the same. Then, I replaced the fuse on the BBxM with the RXEF025. This time, it worked for 20 minutes. However, after that, the display went off. It wouldn't come on even after I turned on/off the BBxM, waited a while etc etc. No result. The fuse gets very hot if I connect the fitVGA to it. (The converter I must report is fine, works with my Laptop HDMI -> VGA monitor). Ideas?

I don't know what to say. I don't think fit-VGA killed your display, it just converts one signals to another… Please check if resolution/update rate of video from your board is compatible with your display.

@Marietto: I too am using the xM, not C4.@Max: No no every component is fine – the xM's HDMI port is fine, the converter is fine, the monitor is fine. No damage done. Its just that the entire arrangement initially worked, now it doesn't. The components themselves are fine.I use the Ubuntu Demo Image at a resolution of 1024×768, 60Hz. The monitor supports that (clearly, because It did work for ~20 mins).

I have left the idea to use the fit-vga converter. Just I've bought the tekkeon portable battery (the best all around) and I've tried to turn on the BB XM and the LCD screen 8" because this battery has two way to give power to the devices,the USB port and another port that can be regulated with a voltage that varies from 5 to 19 V. The problem encountered is that the +5V is unable to power on the fit-vga converter and the BB XM at the same time. For this reason,I have to change my plans. Maybe there is another kind of converter,something like s-vga to vga or s-vga to composite or I can try simply to configure the BB XM with the s-vga.

There is another socket (DC OUT) on the battery. Is it possible to power BB + fit-VGA from this socket (with 5V output of course)? I.e. are you sure there is no output current limitations on battery's USB port?

The BeagleBoard-xM connects fine to a HDMI monitor. Connecting it to a VGA monitor using the fitVGA cable produces no result (like I said, it first worked for 20 mins and hasn't worked ever since ) The fitVGA cable itself is fine, because if I connect it to my laptop's HDMI port on one end and a VGA monitor on the other, I get the picture.2 other things:1) When the BB-xM is connected to VGA monitor using fitVGA: The monitor I can see is getting a signal (I know this because the monitor LED stays green – if it gets no signal it goes into power saving mode and turns orange). So it gets a signal, but no picture.2) I removed the original PolySwitch (RXEF010 Right?) from the BB-xM. But even without reattaching a PolySwitch, leaving the circuit open, if I use HDMI cable and connect it to my HDMI monitor, I get the picture. How is that possible? Isn't the circuit effectively broken?

First of all, thank you for pointing me in the right direction. I changed the output resolution to 800×600 and the entire setup worked straight away. I'll just list my observations here: the line I'm modifying is in a boot.cmd file which looks like 1024x768MR-16@60.

1) As I had reported earlier, 1024x768MR-16@60 worked only once, the first time, and I have never seen it since.

2) Then, based on your suggestion, I tried 800x600MR-16@60 and it worked. No problems, I reset the beagleboard a number of times, turned on/off, no issues.

3) For the heck of it I started playing around with the numbers in the line. I just put in 1024x768MR-16@58 and I dunno why, it worked. The monitor reported it was running and 1024×768, 57 Hz. The GUI I had designed for 1024×768 displayed worked awesome. Great, I though. But then, when I reset the beagleboard, kaput. No display. Ever. Whatever I tried. On/off, unplug/replug, the whole lot.

4) Problem (3) happened with several sets of numbers, such as 1024x768MR-16@50, 1024x768MR-16@65, 1280x960MR-16@60 etc. First working, then never to be seen.

5) At last I tried 1024x768MR-16@75. This one worked, and even lasted across several resets and jiggling about. No issues. Only problem is that, I don't think my monitor is designed to take 75 Hz. I can see a slight flicker (very slight). It was really perfect with 58-60Hz.

So now my request is, that based on these, can you suggest some course of action? Its almost as if my monitor/beagleboard are memorizing the setting I need and making a mental note to not display that on next boot. I guess I could use 75 Hz if I had to, but I don't know if I could end up damaging my monitor.

It’s quite interesting… From information you’ve provided I can make a conclusion that fit-VGA requires more current in your configuration (I don’t know why). In order to resolve this issue you need to replace your PolySwitch with the one with even higher “steady current”/”trip current” parameters. Try RXEF030, RXEF040 or RXEF050 models.

P.S. For test purposes only you can replace PolySwitch with a piece of wire but I _highly_ recommend you to use another model of PolySwitch with higher current.

it’s almost worked. it means that as soon as ubuntu 11.04 makes the boot,I see the textual messages on the screen (I have the AUO A080SN01 v.8 with a custom VGA/S-video adapter board). When the boot phase is complete,the screen goes in AV mode and it stays there forever. Any workaround ?

It’s appropriate time to make some plans for the future and it is time to be happy. I have read this post and if I could I wish to suggest you some interesting things or advice. Perhaps you can write next articles referring to this article. I wish to read more things about it!

Would you suspect that using an externally powered adapter like this one would avoid having to modify anything onboard? I’ve purchased a PandaBoard and though I haven’t tried using and unpowered adapter I suspect I’d run in to the same issues that marietto did?

I think an externally powered adapter from yor first link should work without any modifications. I’m not shure about the second unpowered adapter as I don’t know which components it based on (and, thus, I can’t a datasheet for current consumption).

I’m using the Buildroot 2012.02 with my Beagleboard-xM Rev.C. I would like to re-direct booting traces from the serial console (with minicom) to my HDMI display.
By using the following setting in uEnvtxt:
…
dvimode=1280x720MR-16@60
optargs=”consoleblank=0″
console=”tty0 console=ttyS2,115200n8″
…
I’ve succeeded to get displayed all booting traces but I could’nt see the login command prompt on my HDMI display but only in the serial console. Could you please tell me where I can activate the DVI display to interact with the command prompt?
Thanks in advance!